1. Field of the Invention
The present invention relates to a manually operated tool of the type in which a grip is pivotally mounted in a housing, wherein the grip serves to displace a push rod mounted in the housing in axial direction and in a stepwise manner. The push rod extends through at least one canting block arranged between bearings supporting the push rod. A spring resting on the housing acts on the portion of the canting block through which the push rod extends. The force applied by the spring on the canting block is directed against the direction of displacement of the push rod. An adjusting force periodically exerted by the grip acts on the outer portion of the canting block remote from the push rod. At least one braking block is provided for holding the push rod.
2. Description of the Related Art
Known in the art are various embodiments of manually operated tools with a grip which is pivotable relative to a pistol-like housing of the tool and which serves to move a push rod mounted in the housing in a stepwise manner and in axial direction. Such manually operated tools are described and illustrated, for example in the following publications: British. Patent 703,780; U.S. Pat. No. 4,135,644; U.S. Pat. No. 5,052,243; European Application 108,584; and WO 89/01322.
In manually operated tools of the above-described type, the push rod which carries a piston at its end is usually used for pressing a substance contained in a cartridge out of the cartridge, wherein the cartridge is mounted in or attached to the housing of the tool. By actuating the grip, the push rod including the piston is forced in a stepwise manner into the cartridge and the substance contained in the cartridge is pressed out. Tools of this type are used, for example, in building construction for applying sealing materials, however, other types of applications for these tools are known in the art.
As described in European Application 108,584 and U.S. Pat. No. 4,135,644, for axially displacing the push rod by a periodic movement of the pivotable grip, a toothing is provided on the push rod which is in engagement with a pawl connected to the grip. However, since substantial forces occur at this location of engagement, the components which mesh with each other are quickly worn, so that the tool becomes useless.
As a further development of these tools, as described in British Patent 703,780; U.S. Pat. No. 5,052,243; and WO 89/01322, the push rod was constructed with a smooth surface and a canting block was provided acting on the push rod, wherein the canting block is actuated directly by the grip or through a transmission. The canting block is pressed against a stop by means of a helical spring through which the push rod extends. For example, the stop is the grip when the grip is in its position of rest. When the grip is pivoted, the canting block is inclined relative to the axis of the push rod, so that the canting block is clamped against the push rod and moves the push rod as a result. This mechanism is provided between two bearings which support the push rod.
The possibility described above for displacing the push rod has been found useful. However, it should be noted in this connection that the actuation of the grip and the resulting load acting on the components which are in engagement with each other causes a significant bending stress to act on the portion of the push rod extending between the two bearings. The reaction forces caused by this bending stress in the bearings must be overcome manually, so that a significant portion of the manually applied force must be utilized for overcoming the frictional forces and deformation forces. Without doubt, this is disadvantageous and impairs the efficiency of the tool.